1) Characterize the pre-obese state with regard to energy expenditure, physical activity and body compostion, 2) Identify environmental and phenotype markers for the development of human obesity, 3) Examine the effects of increasing the level of physical activity in pre-obese children on energy expenditure and the subsequent development of obesity and 4) Derive estimate of energy requirements in children based on measurements of energy expenditure, rather than on energy intake data.